Threaded fixing members such as nuts and bolts are used in a variety of applications to attach to objects together. During use and normal operating conditions threaded fixings can loosen and in some situations completely detach. The unintended loosening of a threaded fixing is at best inconvenient and in some situations can have disastrous implications.
Vehicle wheels are generally attached using a threaded fixing such as a wheel nut or bolt and proper wheel maintenance is especially critical on large transport vehicles, such as trucks, carrying heavy loads over extended distances where the wheels are put under considerable stress. Extreme operating conditions together with constant vibration and impacts require the wheel nuts to be checked regularly. If a wheel nut comes loose, the load will be transferred to the remaining nuts and studs which in turn increases their chance of failure. A badly maintained wheel with many loosening nuts could lead to a progressive stud failure with the wheel separating from vehicle. This extremely hazardous situation has been the cause for many accidents and even loss of life.
As part of routine maintenance, all nuts must re-torqued to specification. This is most often carried out using a large torque wrench and is a laborious task with considerable effort and time required. Some operators use a rattle gun on the nuts without loosening them first—a short cut that will over tighten the nuts causing premature wear and increased stress on the studs resulting in tensile failure.
A range of position indicators for wheel nuts are currently in use, particularly by trucking companies who often deploy them across their entire fleets. Furthermore, in some countries, authorities have made the use of position indicators compulsory.
The most commonly available position indicators are made to fit a given size nut and thus have a fixed internal size that is slightly smaller than the target nut size to ensure a tight fit therebetween. When applied, the plastic material stretches to accommodate the nuts dimensions. However, these position indicators can be difficult to put on and often require the use of special tools. Furthermore, the stretching/deformation of the material required to fit the devices can adversely impact on their service life and their performance due to the premature loss of their elasticity. This problem is exacerbated when the devices are re-used and/or when the operating conditions are particularly harsh, such as operating at extremes of temperature and/or where there is substantial exposure to the sun.
The need for a range of different sized position indicators to fit different sized nuts also has an adverse effect on manufacturing and distribution as many different products are required to fit the entire range of nut sizes used in the market. The cost to manufacture, ship, stock and manage a vast range of products, currently leads some suppliers and distributors to handle only the most common sizes. Unfortunately this creates scarcity for the less popular sizes driving up the costs as they must be ordered specifically.
To the extent that adjustable position indicators, that can fit more than one size of nut, have been developed they have been poorly designed, too expensive and/or have lacked the necessary functionality and ease of use to enable them to be successfully commercialised.
The present invention seeks to provide a position indicator that addresses or at least partially alleviates the aforementioned problems.